You might instinctively think that anyone making such an outrageous (and seemingly paradoxical) claim must be either very stupid or very brave. Ian Morris has made exactly such a claim in his new book*. He is certainly not stupid.

An archaeologist by profession and a gifted polymath, Morris has carved out a niche as a big picture thinker who tries to explain why the world is as it is. There are very few people alive who are as knowledgeable about the broad sweep of human history - he has an astounding grasp of the societies and civilisations that have existed across the planet since our species made it through the last ice age more than 10,000 years ago.

Morris' vast erudition, acute intelligence and willingness to make bold arguments make him someone worth listening to, even when he makes such intuitively abhorrent arguments as he makes in his new book.

But the idea is very much worth discussing in an economics column for a number of reasons, not least because economics is too important to be left to economists alone. Every discipline can profit from having its practitioners pop their heads out of their silos from time to time to hear other perspectives, and so too can economists. A helicopter view of all human civilisation over the past 10,000 years provides the best possible long-term perspective.

First off, it needs to be said that Morris is not a monster or an advocate of war. Nor is he insensitive to the appalling suffering that the victims of violence have suffered. Indeed, he writes that he would have been appalled at his own conclusions if he had read them before he had arrived at them. But real scholarship involves not shying away from unpleasant conclusions.

Having made it clear that Morris is no war monger or glorifier of blood sacrifice, let's focus on his thesis. The essence of that thesis is that there are two types of war - productive and unproductive. The unproductive kind results in chaos, disintegration and disorder, much as happened when invaders from the Eurasian steppe caused the collapse of both Ancient Rome and the Han dynasty in China within a relatively short time of each other.

By contrast, the wars Morris considers "productive" are those that bring more people together in larger societies with stronger rulers. The wars that led to the emergence of Imperial Rome and the Han dynasty in China are two examples. He argues that such "productive" war is - almost paradoxically - central to pacifying human societies.

The case that powerful rulers bring lower levels of violence is strong. Among the most fascinating new insights to emerge over the past couple of decades - from archaeology, anthropology and other fields of study - is the very long-term decline in violence in human societies.

The sort of small bands our ancestors lived in for most of human history were constantly raiding and fighting each other. While it was vogueish during much of the last century to believe that people in such societies were placid and peace-loving (at least when compared to westerners, who were claimed to be unusually violent), the accumulated evidence suggests otherwise. From ancient burial sites and during long spells spent with such groups in places where they still exist, such as the Amazon basin, a growing body of evidence points to 10-20pc of all deaths being caused by violence in very small-scale societies.

But as societies become bigger they are almost always governed more hierarchically, with rulers exercising greater power over the ruled. Central to this process is rulers' monopoly on the use of violence. Though rulers in such societies may abuse their monopoly on the use of force, the overall level of violence in such societies declines as people resort to violence less frequently to resolve disputes. Morris estimates that the proportion of people who died at the hands of other people fell to 2-5pc in the larger civilisations that existed 2000 years ago.

Although the pacification trend has not been smooth, it has been moving in the right direction over the centuries, and even in the last century, with two world wars, "only" one in a hundred people globally had their lives extinguished by another human being.

But if Morris' argument about the decline of violence is supported by a great deal of evidence, his claim about prosperity rising in line with larger political units appears much weaker, in part because there is much less evidence on prosperity levels in the past.

As such, Morris does not present nearly enough new evidence to link the size of a political and economic entity to its level of prosperity per person (and that is even if we ignore extreme inequalities, such as slavery, that characterised many past societies). Given that most economic historians have found that when economies have grown in the past, the gains were gobbled up by rising populations rather than higher incomes, Morris' lack of new evidence weakens the entire premise of the book.

Another weakness relates to the two types of conflict he identifies. One the one hand, there are cases of "unproductive wars" coinciding with economic advance - the ever-warring city states of central and northern Italy in the middle ages and early modern times are a particularly notable example because modern capitalism itself is often considered to have emerged there and then.

On the other hand, a "productive" conflict, such as Britain's incorporation of India into its empire, does not appear to have improved the lot of Indians and may well have undermined it owing to the favouring of British manufacturers over their Indian counterparts. (The economic failure of India in its first four decades of independence also undermines the "bigger-is-better" plank of his thesis.)

A further criticism is that Morris' emphasis on size in determining wealth places far too much emphasis on a single factor and ignores the vast number of other factors that determine prosperity levels. Europe in recent times illustrates this well. While it is certainly true that integration, as has happened in the EU, has boosted growth, even the most enthusiastic integrationists would find it hard to argue that Europe's countries would be significantly poorer if the project had not existed. (Ireland, by the by, is an exception owing to its economic model being so dependent on the EU single market.)

All of this makes the thesis of the book essentially unconvincing, and Morris' argument that war has been both productive and destructive is very unlikely to gain traction. Apart from being a fascinating, informative and thought-provoking read, its impact is likely to be confined to heightening awareness of the long-term decline in violence globally. And that can only be welcomed. That the world is becoming more peaceful is a good news story that should be better known.

* "War: What is it good for? The role of conflict in civilisation, from primates to robots"